Blood returning to the heart from the peripheral circulation and the lungs generally flows into the atrial chambers of the heart and then to the ventricular chambers, which pump the blood back out of the heart. During ventricular contraction, the atrio-ventricular valves between the atria and ventricles, i.e. the tricuspid and mitral valves, close to prevent backflow or regurgitation of blood from the ventricles back to the atria. The closure of these valves, along with the aortic and pulmonary valves, maintains the unidirectional flow of blood through the cardiovascular system. Disease of the valvular apparatus can result in valve dysfunction, where some fraction of the ventricular blood regurgitates back into the atrial chambers.
There are several possible structural causes for atrio-ventricular valve dysfunction, including: loss of pliability of the annulus leading to decreased contractibility; widening of the annulus; thickening, shortening or swelling of the leaflets; dilation of the ventricle; elongation or breaking of the chordae tendineae; and elongation of the attachment of the chordae tendineae with the papillary muscles or ventricular wall. Structural abnormalities at one or more of these anatomical sites may eventually lead to loss of coaptation of the leaflets, loss of competence of the valve and decreased efficiency of the heart as a one-way pumping mechanism. When the latter occurs, various signs and symptoms may be seen in patients, including breathlessness or lack of stamina and heart murmurs.
Traditional treatment of heart valve stenosis or regurgitation, such as mitral or tricuspid regurgitation, involves an open-heart surgical procedure to replace or repair the valve. Currently accepted treatments of the mitral and tricuspid valves include: valvuloplasty, in which the affected leaflets are remodeled to perform normally; repair of the chordae tendineae and/or papillary muscle attachments; and surgical insertion of an “annuloplasty” ring. This requires suturing a flexible support ring over the annulus to constrict the radial dimension. Other surgical techniques to treat heart valve dysfunction involve fastening (or stapling) the valve leaflets to each other or to other regions of the valve annulus to improve valve function (see, e.g., U.S. Pat. No. 6,575,971).